1. Field of the Invention
This invention relates to automatic fuel dispensing nozzles, and in particular to automatic nozzles for filling automobile gasoline tanks in which the vapor displaced during the filling operation is recovered.
2. Description of the Prior Art
In order to reduce atmospheric polution and to conserve energy, vapor which is displaced from an automobile gasoline tank during filling at a filling station is often recovered. The displaced vapor is typically recovered through passages formed in the body of the gasoline dispensing nozzles. Examples of prior art vapor recovery nozzles are shown in U.S. Pat. No. 3,974,865, issued to Fenton et al.; U.S. Pat. No. 3,982,571, issued to Fenton et al.; U.S. Pat. No. 4,060,110, issued to Bower; and U.S. Pat. No. 4,143,689, issued to Conley et al. However, there have been various difficulties in the design of previous vapor recovery nozzles.
One difficulty relates to the position of the vapor passage in the body of the nozzle whereby condensate in the vapor passage tends to stay in the nozzle or to drain down into the hose. If the condensate accumulates at a low point in the hose, it may block the vapor passage and thus defeat the purpose of the vapor recovery system.
Another problem with prior art vapor recovery nozzles relates to the ease with which such nozzles may be disassembled and modified. Vapor recovery nozzles are usually inspected and certified by appropriate private and public agencies, such as Underwriters Laboratories, Inc. and state air pollution control boards. These inspections and certifications were intended to certify that the nozzles as originally manufactured meet all necessary requirements in order to function properly. However, the nozzles frequently have been disassembled and modified by the operator or by other individuals. The prior art vapor recovery nozzles have been relatively simple to disassemble because the valve stem could be easily removed from the nozzle and the tripping mechanism could also be easily removed and modified or replaced with inferior parts. Thus, prior art nozzles were not tamperproof, and, as a result, the nozzles were frequently modified so that they no longer performed in accordance with the standards originally met for private and public certification. When reassembled after such modifications, it was virtually impossible to tell that modifications had taken place and that the nozzles no longer met the standards as originally manufactured.
Another problem with gasoline dispensing nozzles in general, and vapor recovery nozzles in particular, relates to a reliable mechanism for stopping the flow of liquid from the nozzle if the nozzle is removed from the fill tank. If the nozzle inadvertently falls out of the fill tube or if the nozzle trigger is inadvertently actuated while the nozzle is not in the tank, fuel can squirt from the nozzle creating a dangerous condition. Prior art mechanisms which were designed to prevent this occurrence such as those mechanisms disclosed in U.S. Pat. No. 4,331,187 and No. 4,343,336, both issued to Trygg, have relied upon modifications to the vacuum tripping mechanism and have permitted some amount of fuel to squirt from the nozzle before the mechanism actuated.
A similar problem is unique to for vapor recovery nozzles. In order for the vapor recovery process to work reliably, it is important that a good seal be made between the vapor recovery shroud and the opening of the fill tank. If the nozzle is barely inserted into the fill tank, the fuel dispensing operation will continue as normal, but the vapor recovery operation will be frustrated because vapor will escape before it enters the vapor recovery shroud. It is important, therefore, that the nozzle be fully inserted into the fill tank before fuel is dispensed.
Another problem with prior art nozzle designs related to the design of the trigger mechanism. The triggers for gasoline dispensing nozzles relied upon an attachment to a tripping mechanism to provide the fulcrum for the trigger. The trigger then engaged the valve stem to open and close the dispensing valve as long as the tripping mechanism did not sense that the gasoline tank was full. This trigger mechanism was relatively difficult to design and involved very close tolerances. In addition, the pivoting action of the trigger on the tripping mechanism produced side forces on the valve stem, and these side forces could bind the valve stem and prevent it from operating under certain circumstances.
While the prior art vapor recovery nozzles have included many improvements over their predecessors, they still had many design features which were not optimum.